Ulysses Spacecraft on its Last Legs

doconnor writes "JPL announced that Ulysses' mission will be ending after 17 years. The power generated by the decay of a radioactive isotope has been slowly decreasing. To conserve power its main transmitter was shut off. Unfortunately due to a fault in its power supply it cannot be turned back on. The team plans to continue operating the spacecraft in its reduced capacity, using the alternate S-band transmitter, for as long as they can over the next few weeks." Congratulations to all the geniuses involved in this one.

Comments

Re:D'oh

[Anonymous Coward]

From TFA:
"- has lasted more than 17 years or almost four times its expected mission lifetime"

Yeah, They only got 4 times the usefullness out their investment as they'd originally hoped to get... They must be furious.

Geniuses

[outlander78]

I'm not sure if the congratulatory statement was sarcastic or sincere, but I hope it was sincere. From the article:

"The joint NASA and European Space Agency Ulysses mission to study the sun and its influence on surrounding space is likely to cease operations in the next few months. The venerable spacecraft, which has lasted more than 17 years or almost four times its expected mission lifetime, is succumbing to the harsh environment of space."

Further on the article states that the lifetime was expected to be five years, so three times, not four, but still, a spacecraft tripling its expected useful life is a strong testament to the skill of its engineers.

Re:Geniuses

[Mr. Underbridge]

This kinda makes me wonder if NASA and other space agencies purposely over-estimate the useful lives of their spacecraft.

I think it's a testament to how difficult it is to estimate the challenges of space exploration. To me, keeping a vehicle operational on another planet we've never set foot on with no opportunity for maintenance sounds damn hard. Doing that for the first time, I imagine 90 days sounded like a stretch. The fact that they've done it for over 3 years to me is one of the great successes of space exploration.

Re:Geniuses

[JohnSearle]

Further on the article states that the lifetime was expected to be five years, so three times, not four, but still, a spacecraft tripling its expected useful life is a strong testament to the skill of its engineers.

Who exactly makes determines the expected life of these things? Is it the scientists who are working on them? 'Cause if you want to be a glass-half-empty kind of guy, then you could say that it's a poor testament to their ability to predict expectancies, rather than to exceed them.

- John

Re:Geniuses

[Anonymous Coward]

The Engineers Credo:
  How long will it take? Double it, then add in a factor of two for contingency.
  How long will it last? Halve it, then take a factor of two for contingency.
  If it moves, oil it. If it doesn't move, hit it with a hammer 'til it does move, then oil it.

Obligatory Trek Quote

Kirk: "How long to re-fit?"
Scotty: "Eight weeks. But you don't have eight weeks, so I'll do it for you in two."
Kirk: "Do you always multiply your repair estimates by a factor of four?"
Scotty: "How else to maintain my reputation as a miracle worker?"
Kirk: "Your reputation is safe with me."
      -- Star Trek III: The Search For Spock

Re:Geniuses

[Vellmont]

This kinda makes me wonder if NASA and other space agencies purposely over-estimate the useful lives of their spacecraft.


There's a hidden premise here. The premise is we can know the expected lifetime of something that:

• We never fully get to test each probe in the environment it experiences.
• We've only made (I'm guessing) less than 100 of these probes ever, each of which is very different and experiences very different environments.
• We don't even know exactly the environment each probe is going to experience.
• The technology itself is constantly changing over the last 40-50 years of sending out robotic probes.

Which do you think is more likely?

The engineers all know how long the thing is going to last, but lie about it to make themselves and NASA look good.

or

They really don't know how long it's going to last, but make some very conservative estimates about the above unknowns, to make sure it'll last at least as long as the time frame it's supposed to. Sometimes those guesses turn out to make the thing last a lot longer than it needed to be.

Re:Geniuses

[v1]

Although this is not a purely NASA project, NASA and every other spacecraft agency severely over-engineer their hardware. Most systems are at least redundant if not double redundant, and they incorporate numerous failsafes, fallbacks, and keep as many options open as possible at all times. If something breaks, unless you have the ability to work around it or fix it remotely, you're done. You can't just send a tech out to fix it.

The rovers on mars almost died when their flash memory filled up, because they did not intend to survive long enough to gather so much data, that the capacity of their flash was deemed more than enough. This alone is good evidence that they aren't really intending for things to run this long, just sometime they do a really good job AND get really lucky. Go read about the Expensive Hardware Lobbing to get an idea of just how easy it is to make a mistake, and how catastrophic such mistakes are. Even with how much care goes into these things, we still don't keep terribly good odds.

I don't know all the reasons the rovers are still running, but I've heard several. The crippling flash space problem was averted because of an automatic reboot, in addition to an automatic failsafe mode, the combination of which allowed them to get in and clear disk space. The rover with the dead wheel, they were able to disengage its motor so it didn't eat up power and drag on the ground (not turning) and that again isn't something you'd necessarily ever expect to need to do, but they added that ability anyway and it paid off. I'd bet there are at least a dozen other "plan ahead" safeties that have saved their bacon too.

From Mariner 2's entry on EHL: On September 8 17:50 UT the spacecraft suddenly lost its attitude control, which was restored by the gyroscopes 3 minutes later. The cause was unknown but may have been a collision with a small object. Then, on November 15, one solar panel failed. However, the probe got within 34,773 km of the planet on December 14 19:59:28.

The odds of it hitting something out in space has to be incredibly slim, but they installed gyroscopes anyway, and as a result were able to continue the mission. You can't really factor that in when trying to calculate the life expectancy of a project like this. All you can do is build it the absolutely best you can, and hope you don't get mugged by too many problems at the same time.

Although the ppl at NASA are certainly skilled, I don't think we can call any of them "experts" at this space exploration thing. They may be the best we've got, but lets face it, there's a lot we still don't know, and we're not able to build experience very quickly. We're total n00bs in space. I don't think we over-estimate anything, we just get lucky now and then. Building in failsafes and options gives us one or two more extra chances sometimes when something we do doesn't work, and that can turn a single 5 year mission into four or five learning experiences before it finally breaks beyond hope, rather than one.

When Mariner 3 failed to eject its heat shield, that one mistake totally screwed the entire mission after a very long wait. Instead of tinkering with various ways to fix the problem remotely with your available options, Game Over. Wait another 5 years and try again. Those are the painful lessons they try to avoid by what is sometimes perceived as over-engineering or under-estimating.

Re:Geniuses

[Adambomb]

Personally I wouldn't even try to compare lunar rovers to planetary rovers, as an environment of extremely predictable temperature, no weather or atmosphere, is definitely a lot easier to work with than even slight amounts of atmosphere and weather (as shown by the martian dust storms, and say, trying to get through venus' cloud layer).

Sarcasm Is Not Recommended.

[cupofjoe]

I'd like to hope that the "geniuses" comment featured in the article post, but I honestly can't tell. I think some of the previous posts point out, better than I can, how unseemly sarcasm would be in this case.

For information on how successful the Ulysses mission has actually been, including its recent historic third pass over the north solar pole, Please refer to the Ulysses home page at JPL:

http://ulysses.jpl.nasa.gov/

In any case, I'd like, perhaps, to suggest that the article post could either have been written, or otherwise reviewed, with more editorial skill. Then again, maybe that's asking too much. And that statement was not intended to be sarcastic.

Cheers,
--joe.

Solar Polar Mission

[mbone]

The mission of Ulysses was to use a Jupiter gravity assist to go out of the plane of the solar system, and
thus observe the Sun from high solar latitudes. It fulfilled that mission and lasted long enough to observe both
the North and South poles of the Sun. I would say it was fully successful.

It is not uncommon for the death of old spacecraft to be messy or even sloppy - the Viking 1 lander was killed by a programming bug -
but that does not detract from their earlier successes.

Re:D'oh

[a_nonamiss]

Millions of dollars for what is now a giant hunk of metal. I sure hope they got something out of the project before transmission was cut off. Hell yeah! Preach it brother! Reminds me of those two hunks of junk they shot up to Mars. I mean, those $820 million tin cans aren't even 5 years old yet, and they're barely running. What a waste of money! My car only cost $15000, and it's been running for 15 years. Someone at NASA really deserves to be fired over these blatant wastes of money.

[/sarcasm]

Kudos to the Ulysses team

[element-o.p.]

I've got to say that I am blown away by this. Look at it in these terms: where I work, we are really proud of the fact that we've got a router that has an uptime of something like 2 1/2 years. It's in a data center in a very remote village in Alaska -- the only way in is via airplane. However, it is reachable, it's in a more or less climate-controlled environment and it has (relatively) stable power.

By contrast, Ulysses is traveling in one of the most hostile environments we can imagine. Everything in the shade is approaching -400F (IIRC) while everything on the side facing the sun is getting blasted with the full fury of solar radiation. There's no way to reach it for maintenance. It's technology is 17 years old now. It has no protection other than its own skin from any micro-meteors it encounters. And it has been running continuously since it was launched. You've gotta admit that's an impressive feat. Yeah, I'd say the NASA engineers responsible for Ulysses are 1) definitely geniuses, and 2) very deserving of congratulations.

Re:D'oh

[sjames]

4 times the usefulness" is a bit of NASA doublespeak.

However, in this case, it really is on the tail end of the extended mission. The reason they wanted to shut the xband transmitter off was that the isotope generator is winding down. The output of the isotope generator is quite predictable. That is, they KNEW it would be out of energy by now. Had they been able to toggle the xband transmitter and divert energy as planned, it would have bought a second extended mission of about 2 years. NASA has done a pretty good job w/ Ulysses.

Meanwhile, given the extreme hostility of space and the complete impossability of making repairs once launched, the practice of overdesign for the primary mission is justifiable. The extended secondary mission is the simple practicality of if it's still working, might as well enjoy it.

Re:D'oh

[dissy]

I can only imagine the fit NASA had when they found this out. Millions of dollars for what is now a giant hunk of metal. I sure hope they got something out of the project before transmission was cut off. Why hope, when you can read and know for sure?

Oh, wait, slashdot... my bad, carry on

Re:D'oh

[Armakuni]

Yeah! And can you imagine how many days in Iraq those millions might have bought us? Like almost a week?

Awesome!

[Anonymous Coward]

This is truly an awesome feat! Ulysses represents what mankind can do when it puts aside its petty differences and works for the betterment of all.

Now, let's shoot it down before the Chinese do!